Inheritance problem

Question

I have a problem with a bank search, I will try to explain in the best possible and clearest way.

I have a table Pessoa and a table Cliente, the last inherits from Pessoa, I also have a table Unidade and a MensagemUnidade.

The Table MensagemUnidade has customer relationship as follows :

public class MensagemUnidade
{
    public int ClienteId { get; set; }
    public int UnidadeId { get; set; }

    public virtual Cliente Cliente { get; set; }
    public virtual Unidade Unidade { get; set; }
}

I am using the DDD(Domain-Driven Design) model in project construction, when I try to do a research on mensagemServico he brings the message, brings the company, and even the ClienteId , but the object Cliente comes void.

I don’t know what I might have done wrong, on the table Client only has the PessoaId I added a person and then added that person to the customer, if I search for that person PessoaId he returns a Cliente, but it does not bring when seeking message.

My Class Cliente does not have any connection class (Ex Unit) but my unit class has a Coleção de Clientes.

If anyone can help me I will be extremely grateful, if information is missing and only and warn.

In the context this contains the following line in the method onModelCreating:

 Configuration.LazyLoadingEnabled = true;

In the example I followed in OnModelCreating of Contexto is using a code similar to that

 modelBuilder.Entity<ClienteLoja>().HasRequired(v => v.Loja).WithMany(m => m.Clientes).HasForeignKey(f => f.LojaId);

I didn’t put anything like this in my code, is it necessary? if yes why?

EDIT: This is the research I do :

 List<MensagemUnidade> mensagens = this.mensagemServico.GetMany(l => l.UnidadeId == unidade.UnidadeAtual && l.OrigemId == (int)enumOrigemMensagem.USUARIO).OrderByDescending(l => l.DataEnvio).Skip(mensagemModel.PaginaAtual * 20).Take(20).ToList();

EDIT 2 : This is the method I use as getMany, there was a previous project here and I need to make a new one and I am using this previous base, in a similar search it brings the necessary information even without the include or something like, everything else is the same as my code except in the context that I have nothing of the kind:

 modelBuilder.Entity<ClienteLoja>().HasRequired(v => v.Loja).WithMany(m => m.Clientes).HasForeignKey(f => f.LojaId);

this and my getMany method:

public virtual IQueryable<T> GetMany(Expression<Func<T, bool>> where)
    {
        return dbset.Where(where);
    }

Answer 1

With the LazyLoad Voce can access the property Cliente content requires that the contexto is still alive.

If you want access to the property Cliente after that will have to load form Eager. In your case this is just the ideal solution to avoid the problem of N + 1

As @Guilherme de Jesus Santos indicated Voce can use the Include. To use the version lambda Voce also needs to include the namespace System.Data.Entity

using System.Data.Entity;

The end result would be:

this.mensagemServico.Include(c => c.Cliente)
    .Where(l => l.UnidadeId == unidade.UnidadeAtual && l.OrigemId == (int)enumOrigemMensagem.USUARIO)
    .OrderByDescending(l => l.DataEnvio)
    .Skip(mensagemModel.PaginaAtual * 20).Take(20).ToList();

The solution Voce has is to change its class mensagemServico. In fact your method GetMany may not even make much sense. I suggested Voce implement a method for each query/process. If this implies many changes in your code at this time let the GetMany where he is.

For example for this case Voce would create the following method:

public IEnumerable<MensagemUnidade> GetMensagensDoUsuario(int unidade, int pagina)
{
     return dbset.Include(c => c.Cliente)
        .Where(l => l.UnidadeId == unidade && l.OrigemId == (int)enumOrigemMensagem.USUARIO)
        .OrderByDescending(l => l.DataEnvio)
        .Skip(pagina * 20).Take(20).ToList();
}

Answer 2

Since you are using Entityframework, I believe you need to add the clause Includewhen you search the entity Mensagem.

By the way today you must be doing something like this :

   var query = from msg in db.MensagemUnidade
            select msg;

In this case, because of the concept of Lazy Loading, the Customer entity will not be loaded.

Then change the query to

 var query = from msg in db.MensagemUnidade.Include(c => c.Cliente)
            select msg;

This way the Client entity is loaded.

This article also explains the behavior : https://ferhenriquef.com/2012/03/19/uso-de-include-em-consultas-com-o-entity-framework-code-first/